Biochemical studies on sulfate-reducing bacteria. XI. Purification and some properties of sulfite reductase, desulfoviridin

Desulfoviridin from Desulfovibrio vulgaris was separated into two forms by DEAE-Sephadex column chromatography. The major form had a p / of 4.4 and the minor form one of 4.5-4.6. Both forms produced mainly trithionate, besides thiosulfate and sulfide, in methyl-viologen-linked sulfite reduction. The specific activities of sulfite reduction, as well as of hydroxylamine reduction, were virtually identical in both forms. There were no great differ-ences in their absorption spectra, CD spectra, molecular weights, subunit compositions, labile sulfide, and iron contents, and amino acid compositions. The N-terminal amino acid was alanine in both forms. Desulfoviridin (1, 2), a green protein isolated from the dissimilatory sulfate-reducing bacteria Desulfovibrio, reduces sulfite (3, 4) which is an intermediary redox-state in the conversion of sulfate to sulfide. The products of the sulfite reduction are trithionate, thiosulfate, and sulfide (4-7), the ratio of which depends on the relative concentra